Bioavailability And Refined Health Risk Assessment Of Polycyclic Aromatic Hydrocarbons In Soil Of Petrochemical Sites

To accurately assess the remediation area of contaminated sites,a human health risk assessment is required.At present,when Chinese researchers conduct health risk assessment,they mainly rely on the total amount of pollutants,which often overestimates the area of site remediation,resulting in high restoration costs and excessive waste of funds.Therefore,in order to overcome these shortcomings,this paper takes soil polycyclic aromatic hydrocarbons(PAHs)in a typical petrochemical site as the research object,simulates the human gastrointestinal digestive environment,evaluates the health risks of PAHs dissolved in the human gastrointestinal tract,and explores the influence of soil physicochemical properties on bioavailability.The research content and results are as follows:(1)Fifteen kinds of PAHs were detected in soil samples at each sampling point,and the total content((50)PAHs)of 15 kinds of PAHs ranged from 547.20～6433.00μg/kg.The average content of ACY,ACE,PHE,ANT,FLO,PYR,FLU,CHR,Ba A,Bb F,Bk F,Ba P,Dah A,Icd P and Bghi P were 51.26、59.22、147.61、40.61、127.25、134.29、60.23、199.53、117.40、166.40、53.19、172.23、120.65、108.83 and 190.34μg/kg.Compared with the relevant research results at home and abroad,the content of PAHs in this study was relatively high.Among them,5～6 ring PAHs were the most common,followed by 4ring PAHs,and 2 ring and 3 ring PAHs were the lowest.The PAHs in the study area were heavily polluted.(2)Four methods(PBET,UBM,SBRC,and SBET)were used to analyze the bioavailability of 15 PAHs in the soil of the study area.The bioavailability of ACY,ACE,PHE,ANT,FLO,PYR,FLU,CHR,Ba A,Bb F,Bk F,Ba P,Dah A,Icd P and Bghi P were 99.00%,47.53%,97.47%,83.88%,63.33%,63.21%,75.01%,69.16%,77.50%,69.55%,77.21%,62.10,77.90,48.20%,48.51%,48.51%,46.31%.(3)After analyzing the correlation between bioavailability and PAHs content of 15 PAHs in the study area,it was found that the background content of PAHs in soil had a significant negative correlation with bioavailability(p<0.05).After analyzing the correlation between physicochemical properties and bioavailability,it was found that SOM and PAHs bioavailability in this study area showed a significant negative correlation(p<0.01).After the correlation analysis of four in vitro gastrointestinal simulation methods,it was found that there was a significant positive correlation(p<0.05)between SBET method and SBRC method,and UBM method and PBET method.So it is recommended that researchers use SBET method to determine the bioavailability of PAHs in soil with simpler and faster operation,simpler composition and shorter simulation time.(4)In the toxicity assessment of PAHs,it was found that two sites exceeded the risk limit,and the carcinogenic equivalent concentration was reduced after bioavailability modification,the number of sites exceeding the safety threshold was reduced by one.The Lifetime carcinogenic risk model(ILCR)was used to assess the carcinogenic risk of PAHs in the soil of the study area through oral ingestion,nasal inhalation,and percutaneous exposure.The results showed that the risk of cancer in the three pathways was in descending order: skin contact > oral ingestion > nasal breathing.In the assessment of carcinogenic risk through oral ingestion in children,the potential carcinogenic risk of oral ingestion was reduced by one sample site after adjusting for bioavailability.Although there was no reduction in potential carcinogenic risk points in adults after the bioavailability modification,the risk of carcinogenesis was reduced by 33.82%.It is necessary to consider bioavailability when evaluating the carcinogenic risk of PAHs in the site.